1. Field of the Invention
The present invention relates to a three-dimensional CAD system and a parts cost calculation system for calculating production costs of parts to be formed by dies based on three-dimensional data about the parts in question. More particularly, the invention relates to a three-dimensional CAD system and a parts cost calculation system for calculating costs of parts in consideration of their drafting directions.
2. Description of Background Art
In recent years there has been a widespread use of systems for calculating costs of parts using computers. For example, Japanese Patent Laid-open No. Hei 9-160945 discloses a system that receives two-dimensional data about parts from a CAD system, extracts cost factors such as the size and shape of the parts from the received two-dimensional data, and calculates the cost of these parts based on the extracted cost factors.
The production costs of parts formed by dies are dependent not only on the size, weight, material and shapes of the parts but also on the cost of the dies to a considerable extent. The bulkier and heavier the dies, the higher their costs. That means the dies should preferably be designed to have the smallest possible volume.
To calculate the cost of a die requires obtaining both a projected area of the part in question on a plane perpendicular to a drafting direction of the die and a depth of the die in that drafting direction. Because conventional systems typically received two-dimensional data from an outside source as mentioned above, if the drafting direction is established anywhere other than with respect to the front, on the side or on top of the die, such a system has a difficulty in calculating the projected area of the part or the depth of the die involved.
Under the circumstances, whenever the drafting direction was set anywhere other than the above-mentioned three directions, the operator performing data input work upon cost calculation was required virtually to establish a drafting direction deemed optimal at his or her discretion and to predict accordingly a projected area of the part in question and a depth of the die involved in order to calculate die costs.
Such conventional procedures required not only many man-hours during data input work but also a high degree of expertise on the part of the operator. There was also a possibility that different drafting directions may be set for a given part by different operators. All this detracted from accurately calculating the cost of the parts.